Grease Is the Word or, How I Taught My Diesel To Drink Veggie Oil and Love It


  • Setting Up

    Setting Up

    The patient up on ramps (jack stands make me nervous) and anticipating the conversion. | March 18, 2010

7 Photos

I have a love/hate relationship with my car.

While my VW TDI is the best vehicle I have ever owned, I despise the fact that it requires fossil fuel that pollutes the environment and increases our need to maintain unsavory relationships with foreign governments. I look forward to the day that I drive an electric car (solar charged, of course), but for now, my transportation choices are limited.

That's why last Sunday, against what most folks would say was sane reasoning, I stood in front of my beloved 2001 Golf and cut the fuel lines in half.

And I did it with a smile on my face.

Running your car for (and on) peanuts The first time I heard about running a diesel car on vegetable oil was in a copy of Home Power, a magazine devoted to "off-grid" living. I was instantly intrigued by the prospect of jumping off the petroleum bandwagon and helping the environment at the same time. I purchased a book on the subject, read it twice for good measure, and was hooked.

In the early 1900s Dr. Rudolph Diesel (1858-1913) designed a new engine that operated on the principle of compression-ignition (diesel engines) rather than spark-ignition (gasoline engines). It was stronger, more efficient and most importantly, designed to run on peanut oil. That's right, peanut oil.

Unfortunately for all of us, Dr. Diesel met with an untimely death a few years later and the peanut oil concept was quickly forgotten. Sensing a vast, emerging market, the oil companies swept in and created a fuel they called "diesel." The rest, as they say, is history.

While diesel engines have changed considerably over the years, it is still possible (even preferable) to run them on vegetable oil. There are two ways to do this:

Biodiesel — Biodiesel is basically vegetable oil (palm, corn, soy, canola, walnut, jatophra and olive to name a few) that has undergone a process called "transesterfication," which removes the triglycerides and thins it out. Biodiesel and diesel can be used interchangeably and can be mixed in any amount. An added benefit of using biodiesel is its solvency, potentially resulting in cleaner and longer-lasting engines.

Waste Vegetable Oil (WVO) — WVO is exactly what it sounds like: vegetable oil that has been used by a restaurant for deep frying and is ready to be discarded. The oil can be picked up (with permission of course), filtered to remove sediment and water, and used as fuel. A cleaner version of this is Straight Vegetable Oil (SVO), which is pure vegetable oil that has been purchased (clean and unused) and does not need any filtering (a bit less messy of course, but tougher on the ol' change purse as it's not free). With the exception of the need to filter WVO, the two are essentially the same.

While biodiesel and WVO have their differences, they can both be made domestically, are renewable and sustainable, add very little net CO2 to the atmosphere and, in almost every way, burn cleaner than diesel fuel. In addition, I've found that neither alternative fuel affects my diesel's relatively high mpg (I average around 40 — unless of course my wife has been driving my car).

To run biodiesel (or B100, as pure biodiesel is called), you simply put it in your diesel tank and away you go (not quite as sexy as I'd like it to sound, but hey, it's the truth). The only modifications that may be necessary are that some older diesels (generally pre-1995, but check your specific make to be sure) will need new biodiesel-rated fuel lines over time.

WVO requires a bit more work. Most folks will speak of "converting" a diesel vehicle to run on vegetable oil but in reality a better description would be "upgrading" it, as you are essentially adding a bunch of stuff that will heat, thin and filter the WVO before it hits the engine. The engine itself is left untouched. Back in the days of Dr. D, engines were much less sophisticated, requiring no modification, but with today's injection engines, cars cannot be started and stopped on WVO.

After a WVO conversion, you start your car on diesel (or better yet, biodiesel), and run it until the engine is nice and hot. At around 180 degrees (many cars have a temperature gauge, but one can be added), you hit a switch, which changes the fuel supply to vegetable oil. Then you drive around for awhile and wonder why you have the munchies all the time. (Yes, it can smell like french fries, tempura, or whatever was fried in the oil...I'd stay away from the fish restaurants if you can.) Just before shutting down, hit the switch again and the fuel supply returns to (bio)diesel, flushing out the combustion chambers and cleaning out any remaining WVO.

Simple, right?

Actually it is, but of course modifying your diesel to run on WVO is another story.

Merging onto the grease highway If you are reading this article and considering going the veggie route, there are several steps you'll want to take.

The first thing you'll want to do is realize that your wife is right, and you are not the mechanic you think you are. Then call your friend Matt in Seattle and tell him what you are thinking of doing. When he stops laughing, beg him to come down and show you what you will be doing wrong. With any luck, Matt will agree, and you can move on to the next order of business.

Next you'll want to figure out what exactly you are going to put under your hood...and in your trunk...and around the wheelwells...and under the seats...and in the dash...oh dear!

While there are quite a few WVO conversion kits, almost all of them begin with the same basic components:

  • Secondary tank — This is an aluminum or plastic fuel tank that holds the WVO and is heated by coolant lines, electrical heating elements, or a combination of both.

  • Solenoids — These are the units that will actually switch back and forth between your startup fuel (diesel or biodiesel) and WVO. Depending on your choice, you can use either a single six-port solenoid or two three-port solenoids.

  • Heated veggie filter — a separate filter for the veggie oil that keeps the engine happy. This is also where the oil will get spiked up to 160 degrees or more before it hits the engine. The heat is almost always coolant fed, but is sometimes augmented by electrical heat as well.

  • Switches and gauges and wires...oh my — a whole slew of wires, nuts, screws, tubing, lock rings and, of course, the fuel-level gauge and the magical switch that will make it all happen.
While I don't want to endorse any particular company as I feel that they all have their pluses and minuses, a simple Googling of "vegetable oil diesel" will give you more information than you can handle. Buying the parts separately will run under $1,000, while a kit can range from $1,000-$2,500 depending on the extras it includes (automation, gauges, tank sizes, etc.).

A good source of info on the process is Sliding Home by Ray Holan. It's an easy read and has a great section that compares the pros and cons of most of the kits available today. I highly recommend it to anyone considering sliding down the grease highway.

Another key to any WVO-powered ride is a good filtration system. After picking up the oil from your local eatery, you'll need to settle it, filter it and, depending on what condition it is in, possibly heat it as well. There are a thousand different designs on the Web for filtration systems you can build at home, but one of the best sources I've found is a DVD called Liquid Gold available through Golden Fuel Systems. While it sounds like a lot of work, filtration is actually relatively painless once you get the hang of it, and a system can set you back as little as $100.

So after reading everything that you can get your eyes on regarding WVO conversions, deciding on the kit you want to go with, assuring your better half that you're not insane and that veggie oil won't kill the catalytic converter (most likely), and spending countless hours on Internet forums where grease truly is the word, hopefully you're ready.

The big changeover I am not a mechanic. While I own a good set of tools, I still hold that everything is a hammer unless it's a chisel and then it's a screwdriver. That said (and with the help of engineer Matt), I set out to change my car for the better.

I'm not going to bore you with the nitty gritty of the whole install here, as there are countless Web chat rooms where you can read about the minutiae of every screw turn of a WVO conversion. That said, I'll hit you with the highlights:

  • Fitted the 15-gallon secondary tank into the spare tire wheelwell.
  • Locked the solenoids and veggie filter in place.
  • Ran coolant lines from the engine back to the tank and back up again.
  • Added new fuel lines incorporating the solenoids and veg filter.
For more photos and details, see here.

Along the way, we found that there is a fair amount of "coaxing" involved in the whole operation, and came to the conclusion that VW engineers must be hired based on the size of their hands as well as on their expertise. Suffice it to say that the engine compartment is a cramped place and the doctor has assured me that all of the skin will eventually grow back.

While we had hoped to finish the project in one day, an incorrectly sized elbow connector pushed it over to Monday. Matt flew back Sunday night and I was left to fend for myself. Luckily most of the remaining work (electrical connections) was fairly straightforward and by Monday night I was ready to go.

I filled up the new tank with pure canola oil (I wanted to start off with SVO so I bought 4 gallons for about $12), and started the engine. The first moments were a bit nerve-wracking as the engine sputtered and stalled a few times, but once all the air had been worked out of the system, my car was back to running as it had before.

Then came the real test: the switchover. I drove the car for awhile until the temperature had been at 190 for a good five minutes (nothing like overkill for the first trial). I hit the switch, the veggie light went on and...

...nothing happened.

Ironically enough, as anyone who has ever done a WVO conversion correctly can tell you, switchovers are the most anticlimactic things you can imagine. Having read about this in my research, I had added a temp gauge in the fuel line just before the engine. Sure enough, after hitting the switch, I watched it steadily climb to 165 degrees. It was running on pure vegetable oil. And it felt great.

Is veggie right for the world? Now a week or so in, my car is running better than ever with no noticeable downside. I've secured permission from a restaurant to take away their used oil, so my fuel is essentially free. They're pretty good about changing their oil frequently so the stuff I pick up every other week is relatively clean, a tad smelly (no worse than an order of fries) and generally amber in color. I've set up a simple filtration system at the side of the house, and after letting the oil heat in the sun for a week or so, I filter out any sediment and it's ready for the car. While I am still in the learning stages and making mistakes as I go (gloves are a good idea at all times and kitty litter sucks up spilled oil like nobody's business), I'm confident that I'll have a good system worked out in no time.

As for the rest of the world, I have to say that WVO is not the final answer. Most people don't want to change the way they drive (switches and gauges may not be for the masses) and hauling around barrels of used fryer oil isn't everybody's idea of a good date (just ask my wife).

There are also those who say that biodiesel and WVO are not all they're cracked up to be. Most will note a higher level of NOx (nitrogen oxide) from the tailpipe. (This creates smog but can be dealt with using additives and emerging technologies.) Some studies show that WVO will eventually destroy a diesel engine, although my friends with 50,000 miles on WVO, who have opened their engines for inspection, would disagree.

In addition, there just isn't enough vegetable oil to go around. If we were to convert all of the planet's fallow ground to fuel crops, we would only cover a small percentage of our transportation needs. That said, for the intrepid few, veggie power is a step toward energy independence and a cleaner environment, and is something that can be accomplished right now.

So there you have it. I guess the only thing left to ask is, "Would you like fries with that?"

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